i know a lot of companies used to sell their old trailers this way......... I know i got one several years back from one of the local smaller carriers......... I use at our business as overflow storage

Matt check with company's that rent storage trailer's they usally buy trailers in lots some are good some need work to remain roadworthey. They usally sell off the one's that need brake's, bearing's etc. We sell all are old trailers for scrap price but the buyer must scrap them and not resale.

I know you said you were using it for storage, so does it have to be 53ft ? If not, consider buying a used cargo shipping container. Fairly inexpensive and extremely sturdy. I found a few on ebay. There are 53 footers out there, it just appears they are harder to locate.